126 ON THE "FLEXURES AND 



When strata are disturbed by the intrusion of trap 

 or granite, or by the passage of veins of those rocks, 

 they sometimes present traces of fracture, at others 

 of flexure, and, not unfrequently, of both united. 

 Here, the operation of force is equally evident as in 

 the preceding cases, while the very nature of that 

 force is also apparent. The cause of the softening of 

 the strata is here also probably to be sought in that 

 heat to which the very origin of these intruding 

 rocks must be attributed, and of which the effects are 

 also the moving powers in question. The case from 

 Lunga, already quoted, is of this nature. The north- 

 east coast of Sky presents also examples of the same 

 kind, which are particularly explicit and interesting ; 

 as well from their number as from their variety and 

 distinctness. In the clear and extensive natural sec- 

 tions produced by these lofty cliffs, the original and 

 undisturbed condition of the level strata, consisting 

 of limestone, shale, and sandstone, is in many places 

 traced with the same ease as if they were exhibited 

 in a model. The intrusion of the trap is equally 

 visible in others ; presenting every modification of 

 the joint disposition of these different classes of rock, 

 that has yet been recorded wherever these phenomena 

 have been observed. Here, the marks of force ex- 

 erted are seen under numerous shapes ; and, among 

 others, huge fragments and portions of strata are 

 found, not merely broken, but far removed from 

 their original connexions, and, in many places, in- 

 curvated to a considerable degree. These occur- 

 rences, not only therefore prove the actual existence 

 of moving forces, and show the extent and nature of 

 their power, but, at the same time, demonstrate that 

 the heat which accompanied the intrusion of the trap, 



